Last week's firebombing of a UK migrant processing centre was motivated by "terrorist ideology", counter terrorism police said on Saturday.
Police said evidence -- including from devices -- suggested "an extreme right-wing motivation behind the attack" in the southeast port town of Dover on October 30.
The evidence recovered "indicates the attack... was motivated by a terrorist ideology," police said.
Homemade incendiary devices were thrown at the Western Jet Foil Border Force centre, leaving two staff with minor injuries.
The facility in the busy town processes migrants who have crossed the Channel from northern Europe in small boats.
Tim Jacques, senior national coordinator for Counter Terrorism Policing, said that while there were "strong indications that mental health was likely a factor", he had concluded that the "suspect's actions were primarily driven by an extremist ideology".
These met the "threshold for a terrorist incident", he said.
The attack was carried was out by a 66-year-old man who was later found dead
"There is currently nothing to suggest the offender was working alongside anyone else and there is not believed to be any wider threat to the public," police said.
The British government is currently grappling with how to deal with a record number of migrants crossing the Channel from northern Europe in small boats.
- 'Highest vigilance' needed -
Since the beginning of the year, an unprecedented 38,000 people have made the perilous journey, the government's home affairs select committee was told on October 26.
Britain's Home Secretary Suella Braverman this week caused outrage -- and earned a rebuke from the new UN rights chief -- for describing the arrivals as an "invasion".
"Very serious that far right extremism drove this attack," Yvette Cooper, the main opposition Labour Party's home affairs spokeswoman tweeted.
"There must be highest vigilance on potential terror or extremist attacks," she added.
Jo Cox, a Labour Party MP was killed by a far-right extremist just before Britain voted in the Brexit referendum to leave the European Union in 2016.
A parliamentary intelligence and security committee report said in July that a "small minority at the extremist end of the (far right) movement have engaged in racially and politically motivated violence which has increasingly morphed into terrorism".
It cited the murder of Cox and a series of London nail bombings carried out by neo-Nazi militant David Copeland in 1999.
Three people died and scores more were injured in the nail attacks which targeted black, Asian and LGBT people
The report added that the extreme right wing terrorism picture in the UK was "fragmented and complex" but said the threat was "increasingly driven by the internet".